Controversies in fluid therapy: Type, dose and toxicity

Abstract

Fluid therapy is perhaps the most common intervention received by acutely ill hospitalized patients; however, a number of critical questions on the efficacy and safety of the type and dose remain. In this review, recent insights derived from randomized trials in terms of fluid type, dose and toxicity are discussed. We contend that the prescription of fluid therapy is context-specific and that any fluid can be harmful if administered inappropriately. When contrasting ‘‘crystalloid vs colloid’’, differences in efficacy are modest but differences in safety are significant. Differences in chloride load and strong ion difference across solutions appear to be clinically important. Phases of fluid therapy in acutely ill patients are recognized, including acute resuscitation, maintaining homeostasis, and recovery phases. Quantitative toxicity (fluid overload) is associated with adverse outcomes and can be mitigated when fluid therapy based on functional hemodynamic parameters that predict volume responsiveness and minimization of non-essential fluid. Qualitative toxicity (fluid type), in particular for iatrogenic acute kidney injury and metabolic acidosis, remain a concern for synthetic colloids and isotonic saline, respectively. Physiologically balanced crystalloids may be the ‘‘default’’ fluid for acutely ill patients and the role for colloids, in particular hydroxyethyl starch, is increasingly unclear. We contend the prescription of fluid therapy is analogous to the prescription of any drug used in critically ill patients.

Keywords: Fluid therapy; Resuscitation; Critical illness; Peri-operative; Toxicity; Saline; Crystalloid; Colloid

Core tip: Fluid therapy is exceedingly common in acutely ill patients; however, numerous questions on the efficacy and safety of fluid therapy in terms of the type and dose remain. Fluid therapy prescription is context-specific and any fluid type can be harmful if administered inappropriately. When considering crystalloids versus colloids, differences in efficacy are modest but the risk of kidney toxicity and bleeding complications with hydroxyethyl starch appear more significant. The differences in chloride load across crystalloid solutions appears to have physiologic and clinically important effects, in particular for contributing to hyperchloremic metabolic acidosis, kidney injury and greater utilization of renal replacement therapy associated with 0.9% saline. Fluid therapy should be viewed as analogous to the prescription of any drug in acutely ill patients.